1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
2NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
3NorthWest Research Associates, Socorro, NM 87801, USA
4Department of Physics, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA
5Wegener Center for Climate and Global Change and IGAM/Institute of Physics, University of Graz, 8010 Graz, Austria
6Lamont–Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
Received: 22 May 2014 – Discussion started: 15 Aug 2014
Abstract. Continuous measurements of total ozone (by Dobson spectrophotometers) across the contiguous United States began in the early 1960s. Here, we analyze temporal and spatial variability and trends in total ozone from the five US sites with long-term records. While similar long-term ozone changes are detected at all five sites, we find differences in the patterns of ozone variability on shorter timescales. In addition to standard evaluation techniques, STL-decomposition methods (Seasonal Trend decomposition of time series based on LOESS (LOcally wEighted Scatterplot Smoothing)) are used to address temporal variability and "fingerprints" of dynamical features in the Dobson data. Methods from statistical extreme value theory (EVT) are used to characterize days with high and low total ozone (termed EHOs and ELOs, respectively) at each station and to analyze temporal changes in the frequency of ozone extremes and their relationship to dynamical features such as the North Atlantic Oscillation (NAO) and El Niño–Southern Oscillation. A comparison of the fingerprints detected in the frequency distribution of the extremes with those for standard metrics (i.e., the mean) shows that more fingerprints are found for the extremes, particularly for the positive phase of the NAO, at all five US monitoring sites. Results from the STL decomposition support the findings of the EVT analysis. Finally, we analyze the relative influence of low- and high-ozone events on seasonal mean column ozone at each station. The results show that the influence of ELOs and EHOs on seasonal mean column ozone can be as much as ±5 %, about as large as the overall long-term decadal ozone trends.
Revised: 11 Dec 2014 – Accepted: 07 Jan 2015 – Published: 13 Feb 2015
Petropavlovskikh, I., Evans, R., McConville, G., Manney, G. L., and Rieder, H. E.: The influence of the North Atlantic Oscillation and El Niño–Southern Oscillation on mean and extreme values of column ozone over the United States, Atmos. Chem. Phys., 15, 1585-1598, doi:10.5194/acp-15-1585-2015, 2015.